Juni 2024:
neue Veröffentlichung:
Latif, M., Martin, T., & Bielke, I. (2024). Regional variation in extratropical North Atlantic air-sea interaction 1960–2020. Geophysical Research Letters, 51, e2024GL108174. https://doi.org/10.1029/2024GL108174
Abstract:
The relationship between the sea-surface temperature (SST) and air-sea heat exchange, is studied over the extratropical North Atlantic (NA) for late boreal winter during 1960–2020. This relationship provides information about the roles of atmospheric and oceanic processes in driving SST variations. We consider two regions, the central-midlatitude (35°N–50°N) and subpolar (50°N–60°N) NA. Over both regions, the atmosphere tends to drive the variations on the short interannual timescales. On the longer decadal timescales and over the central-midlatitude NA, oceanic processes tend to drive the SST anomalies that in turn influence the air-sea heat exchange. Air-sea heat exchange over the subpolar NA is mostly driven by the North Atlantic Oscillation on interannual and decadal timescales, which is the leading mode of internal atmospheric variability in winter. This study suggests that the atmosphere is more sensitive to SST over the central-midlatitude than subpolar NA.
Time series of sea-surface temperature (SST) and turbulent heat flux (THF) indices in the central-midlatitude North Atlantic (NA) (a), (c) and subpolar NA (b), (d). SST (red scale), and sensible (SHF), latent (LHF) and total turbulent heat flux (THF) (blue scale) for ICOADS (a), (b) and ERA5 (c), (d) for JFM means (thin) and 11-year running means (bold). Negative (positive) THF indicates oceanic heat loss (gain). The time series are not detrended.
Mai 2024:
neue Veröffentlichung:
Luiz, E. W., & Fiedler, S. (2024) Global climatology of low-level-jets: Occurrence, characteristics, and meteorological drivers. Journal of Geophysical Research: Atmospheres, 129, e2023JD040262. https://doi.org/10.1029/2023JD040262
Abstract: In this study, we investigated low-level jets (LLJs), and strong winds in the lower atmosphere that have significant environmental and societal impacts. Using a comprehensive weather data set spanning from 1992 to 2021, we created a global map of LLJs, categorizing them into three regions: non-polar land (LLLJ), polar land (PLLJ), and coastal (CLLJ). LLJs associated with temperature inversions were very common over land, but PLLJs were much more frequent. PLLJs were also the strongest and lowest. Coastal LLJs were prevalent on west coastlines and exhibited changing vertical temperature characteristics. On average, LLJs occurred 21% of the time globally, with higher frequencies over land (32%) compared to the ocean (15%). Regional trends in LLJ frequency and intensity varied, with some areas experiencing more intense LLJs without changes in frequency while others presented an increase in both. The study emphasized the uncertainty surrounding the influence of LLJs on climate and weather extremes in a warming world, with future research aiming at exploring LLJ trends and their broader implications.
Spatial patterns of LLJ characteristics. Shown are the averages of the (a) wind speeds and (b) heights in the core of LLJs calculated as composite means over all detected LLJs, and (c–f) the differences in the characteristics in the mean for December, January, and February (DJF), and for June, July, and August (JJA) relative to the annual means shown in (a) and (b). The dashed areas mask regions where the LLJ frequency of occurrence was smaller than 15%. The results are based on ERA5 for 1992–2021.
